The long term objectives of this research project are to elucidate some of the intracellular mediators through which psychotropic drugs regulate neuronal function. The central focus of the project will be to study the role played by G-proteins, second messengers, and protein phosphorylation systems in mediating the acute and chronic effects of opiates in the central nervous system. Opiates have already been shown in preliminary studies to regulate, both acutely and chronically, certain G-proteins, adenylate cyclase activity, cyclic AMP-dependent protein kinase activity, and phosphorylation levels of a number of individual phosphoprotein substrates for this protein kinase in the locus coeruleus, a noradrenergic brainstem nucleus that appears to be involved in some of the effects of opiates in animals, including humans. The proposed studies are designed to further characterize opiate- regulation of these various pathways, as well as to identify and characterize opiate-regulation of other intracellular pathways, notably pathways involving calcium. The regional distribution and pharmacological specificity of opiate regulation of these various intracellular pathways will be investigated, as well the effects of opiate withdrawal and of pharmacological interventions known to influence withdrawal. Particular attention will be focused on individual phosphoprotein regulated by opiates in order to characterize these proteins with respect to their biochemical, anatomical, and physiological properties. By studying these intracellular pathways, much can be learned about the precise molecular steps underlying acute and chronic opiate action, including steps underlying the development of tolerance, dependence, and withdrawal. Studies employing similar approaches and methodologies will be aimed at identifying intracellular mediators of imipramine (and other antidepressant medications) and cocaine--drugs that regulate the reuptake of monoaminergic neurotransmitters--in order to better understand not only the therapeutic actions of these drugs, but also the biochemical basis of cocaine's extraordinary abuse potential.